This disclosure relates to methods of manufacture of polyetherimide compositions.
Polyetherimides (“PEIs”) are amorphous, transparent, high performance polymers having a glass transition temperature (“Tg”) of greater than 180° C. PEIs further have high strength, heat resistance, modulus, and broad chemical resistance, and therefore are widely used in applications as diverse as automotive, telecommunication, aerospace, electrical/electronics, transportation, and healthcare. One process for the manufacture of polyetherimides is by polymerization of alkali metal salts of dihydroxyaromatic compounds, such as bisphenol A disodium salt (“BPANa2”), with a substituted bis(phthalimide) such as a bis(halophthalimide). For example, polyetherimides can be produced by polymerization of BPANa2 with 1,3-bis[N-(4-chlorophthalimido)]benzene (“4-CIPAMI”), which has the following structure.

Other isomers of the CIPAMI can also be present. Substituted bis(phthalimides) such as bis(halophthalimide)s, in turn, can be produced by imidization of a substituted or halophthalic anhydride such as 3-chlorophthalic anhydride (“3-CIPA”), 4-chlorophthalic anhydride (“4-CIPA”), or mixtures thereof with an organic diamine such as m-phenylenediamine (“mPD”) or p-phenylenediamine (“pPD”).
The polymerization is typically carried out between a dialkali salt of a bisphenol with a bis(halophthalimide) in an aromatic solvent in the presence of a polymerization catalyst. Attempts have been made to produce polyetherimides without using any catalyst to lower the manufacturing costs of the polymer. However, such processes require the purification and isolation of the substituted intermediate bis(phthalimide), which is cumbersome and not desirable in a commercial setting.
Thus there remains a need in the art for an improved process for the manufacture of polyetherimides that does not require a polymerization catalyst. It would be a further advantage if a substituted bis(phthalimide) can be made and used directly in the displacement polymerization without isolation and purification.